Abstract : The hardware composition and GIS software development of vehicle navigation in vehicle remote terminal instrument are discussed. The circuit diagram with SH7764 microprocessor of Renesas Electronics as the core is given, and the architecture and data management of the embedded electronic map are discussed. It also introduces the process of secondary integration development under MapXMobile. This system has been running on the experimental car of Shanghai Pan Asia Automobile Technology Co., Ltd. for two years. It has actually proved that the system is reliable and can meet the basic needs of production.
The main function of the vehicle remote diagnostic instrument is navigation. The focus of the navigation function is driving route design, automatic vehicle positioning, comprehensive information service, route guidance service, etc. Navigation function is a comprehensive application system combining GIS technology, communication technology, embedded technology and GPS positioning technology. The system can achieve accurate and real-time tracking of vehicles through the characteristics of GPS positioning all-weather, high precision and strong real-time. Through the application of GLS technology, the vehicle's positioning information can be displayed on the electronic map to clarify the exact location of the user. Based on the introduction of the typical hardware and software components of the navigation system, the paper focuses on the design and implementation of the car navigation electronic map, which has practical significance for the further optimization of car navigation.
1 Architecture of car navigation electronic map
1.1 System hardware design
When the embedded system is used as the carrier of the electronic map, the hardware system needs to use a 32-bit microprocessor and the operating frequency is above 400 HMz in order to be able to handle a large amount of data and run the operating system smoothly. The hardware system needs to be able to support multimedia functions, support LCD touch screen input, and have a large-capacity SD card loading function. The selected operating system should have information database and map database management functions.
As the core processor of the diagnostic instrument, SH7764 has a maximum operating frequency of 324MHz and can achieve 583MI / S processing performance. The FPU supports single and double precision calculations and can achieve the highest performance of 2.3GFLOPS. And has a wealth of hardware resources, including hardware audio decoding function, Zheng Xuan / Yu Xuan operation and vector element arithmetic operation function. Peripherals perform storage functions including NAND flash memory controller and memory card controller, Ethernet controller (10 / 100BASE-T), USB interface (full speed / high speed), I2C bus interface, serial communication interface with FIFO, display Supporting functions are provided by 2D graphics engine, LCD controller and digital RGB output function.
SH7764's high-speed data processing performance and rich peripheral functions make SH7764 processor a high-performance vehicle diagnostic processing system at low cost. When SH7764 is used to form a vehicle-mounted remote diagnostic instrument, the circuit block diagram is shown in Figure 1.
Figure 1 The circuit block diagram when using SH7764 to form a vehicle-mounted remote diagnostic instrument
1.2 Operating system
The WinCE operating system is a powerful, tailorable, and easy-to-transplant system, and has the storage and management functions of the user information database and digital map database necessary for the system.
In the WinCE operating system, the virtual private network (Virtual Private Network, VPN) is more operable and applicable. It mainly uses the public network as a medium for user information transmission, through additional tunnel encapsulation, information encryption, user authentication Access control and other technologies realize the security protection of the information transmission process, thereby providing users with similar private network security performance. Relatively speaking, the security has been greatly improved, so this network-based information security system generally uses a complex password authentication mechanism to ensure the security of the system account. The system adopts strict authority management to ensure the safety of system operation.
(1) Network operating system layer: Through the network and operating system management mechanism and with the help of corresponding management software and firewall technology, viruses and hackers are prevented from invading the enterprise information management network, and important data and transmitted data are encrypted to prevent Illegal personnel log into the database and application system to ensure the smooth progress of various businesses in the network environment.
(2) Database system layer: through the database operating system ORACLE and other management mechanisms and corresponding management software, to achieve the inspection of the logged-in database users, control of various data operation permissions, timely backup of data and management of historical data.
(3) System application layer: It is mainly the management function test provided by the system platform, including function permission setting, data permission setting, time permission setting, application control mechanism and operation log management.
1.3 GIS software design
The design basis of GIS software lies in the definition of data structure and database structure, which directly determines the stability, rationality, functional integrity, and scalability of the system. The query and retrieval function, image function and analysis function of the GIS software are developed in order.
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